I've also used a bucket hung from the main halyard to scare birds away when they seemed to have taken to roosting on the boom:
But, the most useful thing I use the buckets for is a quick wash down after a swim. I keep one of these five gallon buckets filled with fresh water in the corner of the stern and use a small container for a quick freshwater rinse after a swim. So I find these buckets very useful on board. They are pretty durable but, eventually one might crack or I lose the cover and it has to be replaced. So earlier this spring I went online to look for a replacement cover for one of the buckets and I found a few things that improve my use of these ubiquitous buckets on board. First I discovered the Hydrofarm HG5G 5-Gallon Black Bucket. It is not so much an improvement as a change of color but, the ramifications are that the black color warms the water up faster for that after swim rinse.
The next bucket item I found which was a real improvement was Custom LeatherCraft 1140 EasySeat Lightweight Plastic Bucket Seat for 3 1/2- 5 Gallon Buckets:
This allows one to use the bucket as a seat and works very well for that function as well as a cover for the bucket. It also has a very light coefficient of friction so you can sit on it and spin around on the bucket. Very useful when working down low and needing to turn and reach for a tool. The cover is also has grooves so that it drains off any water that falls on it unlike the usual bucket cover. It also has a very convenient tab on the side that was probably put there so these covers could be hung up for an in store display:
But, I found it very useful to tie a lanyard to the tab and the bucket so the cover could not be separated and fall over the side. Which could easily happen with the generic bucket cover:
I like how this cover worked so well I bought a second one to use on a bucket I have inside the cabin. One would think it's hard to improve on the basic five gallon bucket but, in my opinion someone has.